const fp = require('lodash/fp')
// 数据
// horsepower 马力， dollar_value 价格， in_stock 库存
const cars = [
    { name: 'Ferrari FF', horsepower: 660, dollar_value: 700000, in_stock: true},
    { name: 'Spyker C12 Zageto', horsepower: 650, dollar_value: 648000, in_stock: true},
    { name: 'Jaguar XKR-S', horsepower: 550, dollar_value: 132000, in_stock: true},
    { name: 'Audi R8', horsepower: 525, dollar_value: 114200, in_stock: true},
    { name: 'Aston Martin One-77', horsepower: 750, dollar_value: 185000, in_stock: true},
    { name: 'Pagani Huayra', horsepower: 700, dollar_value: 1300000, in_stock: true},
]

// 使用帮助函数_average重构averageDollarValue, 使用函数组合的方式实现
let _average = function (xs) {
    return  fp.reduce(fp.add, 0, xs) / xs.length
} // <- 无需改动

// let averageDollarValue = function (cars) {
//     let dollar_values = fp.map(function (car) {
//         return car.dollar_value
//     }, cars)
//     return _average(dollar_values)
// }

// 使用fp.flowRighr进行函数组合
let averageDollarValue = fp.flowRight(_average, fp.map(car => car.dollar_value))

console.log(averageDollarValue(cars));